As the automation of human society progresses, there is a need for energy to power more and more modern electrical devices of various sizes. Although nuclear energy has shown its potential to solve this problem, currently available nuclear conversion technologies suffer from inherent inefficiencies and problems. For example, the two-step nature of the conversion process and the limitations of the thermodynamic cycle consume as much as 90% of the initial nuclear energy in its conversion to electricity.
One area of ongoing research is in the area of nuclear batteries. Based on the discovery in 1954 that p-n junctions can generate electric current from beta particles and alpha particles emitted from radioactive materials, as disclosed in Rappaport P., “The electron voltaic effect in p-n junctions induced by beta particle bombardment,” Phys. Rev. 93, 246 (1954) which is herein incorporated by reference in its entirety, research has continued for many years investigating a wide variety materials and techniques to construct nuclear batteries with higher efficiencies as disclosed in Kherani, N. P., et al., “Tritiated amorphous silicon for micropower applications,” Fusion Tech. 28, 1609 (1995), Lai, R., et al., “A nuclear microbattery for MEMS devices,” Proc. 9th International Conference on Nuclear Engineering, Nice, April, 2001, and Bower, K. E., et al. (eds), Polymers, Phosphors, and Voltaic for Radioisotope Microbatteries, CRC Press, Boca Raton (2002) which are all herein incorporated by reference in their entirety.
The physics of direct conversion from nuclear energy to electric current is illustrated in FIG. 1. Basically, a potential difference is maintained by a voltage source V between a positive and a negative electrode while a charged particle is emitted by an unstable nucleus of a radioactive material. The emitted charged particle creates electron/hole pairs that migrate towards the positive and negative electrodes. A resistive load R completes the circuit so that the positive and negative charges which have migrated recombine and power is generated by this induced current flow in the completed circuit.
An apparatus and method for generating electrical current from a nuclear decay process of radioactive material is disclosed in U.S. Pat. No. 6,744,531 to Gadken, which is herein incorporated by reference in its entirety. This apparatus includes a plurality of junction regions formed by the appropriate construction of a number of p-type and n-type dopant sites. At least a portion of one of the junction regions is disposed in a porous region having an aspect ratio of greater than about 20:1 and is disposed at an angle of greater than about fifty-five degrees measured relative to the surface area in which it is formed. Although this apparatus and method is effective, even further efficiencies and greater performance are desired.